Device for fuel injection in internal combustion engines



June 1955 -F. K. H. NALLINGER 2,711,720

DEVICE FOR FUEL INJECTION IN INTERNAL COMBUSTION ENGINES Filed May 31,1951 United States Patent DEVICE FOR FUEL INJECTION IN INTERNALCOMBUSTION ENGINES Friedrich K. H. Nallinger, Stuttgart, Germany,assignor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim,Germany Application May 31, 1951, Serial No. 229,018

Claims priority, application Germany May 31, 1950 7 Claims. (Cl.123-119) This invention relates to a method and device for fuelinjection in internal combustion engines.

Fuel injection without the employment of compressed air, i. e., by thesolid injection method, has the disadvantage that very small injectionnozzles or injection nozzles with very small spray holes must be usedwhich are liable to choke very easily.

On the other hand, the use of compressed air for the injection of fuelis, in the hitherto usual injection methods, attended by thedisadvantage of requiring an additional expenditure for the means forcompressing the air. Furthermore, a relatively high pressure must beemployed in order to ensure a sufliciently thorough atomizing of thefuel.

It is a primary object of the present invention to overcome thesedisadvantages of the known fuel injection systems and, at the same time,to combine the advantages of both methods.

A further object of the present invention is to bring about an effectivepreparation of the mixture to be burned by simple inexpensive meansrequiring, at the most, but few additional parts.

A feature of the present invention therefore essentially lies thereinthat air is admixed to the fuel prior to, or while it is put underpressure, or also subsequently to that period, and the fuel-air mixture,eventually in the form of a fuel-air emulsion, is delivered to theinjection nozzle under pressure.

According to another feature of the present invention the fuel-airmixture is accurately metered and delivered to the injection nozzle bymeans of an injection pump which is so constructed that the mixturevolume inducted by the injection pump is completely. displaced from thepump space.

One particular advantage of the present invention is that, on the onehand, additional means for producing compressed air is rendered almostsuperfluous thus eflfecting considerable saving of expense and, on theother hand, a very eiiective intimate mixing of fuel and air is alreadyeifected prior to their passage through the crosssectional area of theinjection nozzle and, furthermore, very small nozzle cross-sectionswhich are difficult to manufacture and liable to choke easily areobviated owing to the increased injection volume as compared with thatof purely solid injection.

The accompanying drawings illustrate one embodiment of the presentinvention. The fuel is drawn from a reservoir 1 through a fuel line 2and a suction valve 3 by a piston 4 of a delivery pump 5 and deliveredto an injection pump 8 through a delivery valve 6 and a fuel line 7. Theinjection pump 8 comprises in a known manner two pistons 9 and 10 ofwhich the piston 9 is operated on the up-stroke by a cam on a pump shaft11 and on the down-stroke by a spring 12. The piston 9 is permanentlyinserted into or-secured to a sleeve 13 which forms a part of the pistonand in its upper portion extends beyond the piston 9. In thissleeve-like extension the piston 10 slides with friction. Thedown-stroke of the latter is limited by a settable stop 14 and theup-stroke by a resilient stop 15. A delivery line 16 leads to theinjection nozzle 17 which, for example, is held on its seat by means ofa spring 18. The pumpspace 22 formed mainly by the pistons 9 and 13 isprovided with a suction opening 21 and a pressure opening 23.

Provision is made in the suction system of the ,injec tion pump formeans whereby air can be admixed to the inducted fuel. In the diagramillustrated on the drawing this mixture is accomplished, for example, bythe delivery pump 5, the pump space of which is in communication withthe atmosphere by means of an additional suction valve 19 and forexample, a settable throttle 20. Consequently, during the suction strokeof the delivery pump 5 air will be inducted or drawn in through thethrottle bore 20 and suction valve 19 at the same time as the fuelthrough the valve 3, and then the ensuing mixture is delivered throughthe line 7 to the injection pump. By employing appropriatelyproportioned springs which exert their tension upon the valve 3 and 19to hold them on the seats, or by adjusting, or exchanging the throttlebore 29 the fuel-air mixture can then be regulated so as to have themost suitable proportion for injection.

Instead of a throttle bore 20 on the pump 5 there may, of course, beemployed a separate, for example, foamforming mixing device consistingof sieves or the like, and this mixing device may be arranged on thedelivery pump, or on another point of the suction system of theinjection pump, eventually, just in the delivery line thereof.

The injection pump 8 operates in a manner whereby on the down-stroke ofthe pistons 9 and 13, under the action of the spring 12, the upperpiston 10 is carried with it by friction in the manner of a dummy pistonuntil it is arrested by the stop 14 thereby effecting, during thecontinuing downward travel of the piston 9, induction of the fuel-airmixture into the pump space 22 through the opening 21 in the sleeve 13.Subsequent to the closing of the suction opening 21 leading towards theline 7 the fuel-air mixture, enclosed in the pump space 22, is movedupwardly on the up-stroke of the pistons 9 and 13 in that the piston 10is carried with it until the latter, after opening of the pressure bore23, pushes against the re siiient stop 15 whereby the air volumeenclosed in the pump space 22 is displaced towards the injection nozzleby the reciprocating motion of both pistons 9 and 10 and then injectedinto the combustion chamber after the injection valve has been opened.The spring of the stop 15 is so proportioned that the requisite pressurefor the displacement may be built up in the pump space 22. By

such an arrangement, which will bring about that the pistons 9 and 14}are brought very close together, the eifect is obtained that no residueof the fuel-air mixture will remain in the pump space whereby anaccurate control of the amount of fuel is rendered possiblenotwithstanding the admixture of air. The fuel control is preferablyaccomplished by setting the stop 14, for example by means of a rack (notshown) whereby the upper piston 10 is retained in a more or less lowposition during the suction stroke of the pump.

Any other type of injection pump may also be employed instead of thedouble piston pump 8 but preferably only such a pump which again fullydisplaces the inducted fuelair volume from the pump space into thedelivery line, or eventually into a by-pass line.

. Injection into the combustion chamber may, moreover, also beaccomplished by the employment of additional compressed air which, forexample, is delivered directly to the nozzle 17 in such a manner thatthe fuel-air mixture, metered and delivered by the injection pump, is

mixed with the compressed air, which has been delivered to the nozzle,and atomized into the combustion chamber.

Along with this the delivery of the fuel-air mixture may take place atsuch a point in the compressed air stream in which acceleration isimparted thereupon.

Mixing of fuel and air prior, during, or consecutively to the time theyare subjected to pressure may take place in such a manner and in such aproportion that an emulsion of fuel and air is produced.

The invention is applicable to Diesel engines having direct, orpre-combustion chamber fuel injection, or also to engines having fueldistributing systems for the injection of light (volatile) fuels. It issuitable for all purposes, for example, also for automotive-typeengines.

It will be obvious that the details of construction may be varied fromthose shown in the drawings. I therefore do not limit myself to suchdetails.

What is claimed is:

1. Device for fuel injection in internal combustion engines comprising,a fuel supply, an injection pump, an injection nozzle, adjustable valvemeans for mixing atmospheric air with the fuel fed to said injectionpump between said fuel supply and said injection pump to deliver amixture of fuel and air to the pump, said injection pump comprising acylinder, two spaced plungers in alignment with each other, saidplungers sliding in said cylinder and enclosing the pump spacetherebetween, the stroke of one of said plungers being adjustable, adelivery pipe extending to said injection nozzle, and operating meansfor impelling both plungers in such a manner that both plungers arepositioned closely one adjacent the other at the end of the compressionstroke of the pump to thoroughly displace the mixture from said pumpspace into said delivery line.

2. Fuel injection device according to claim 1 wherein said impellingmeans for said pump plungers comprise, a cam-shaft for impelling one ofsaid plungers, a spring for returning said one plunger, a sleeveconnected with said one plunger and operative to carry the other pistonwith it by means of friction, an adjustable stop means for varying theinjected quantity of fuel mixture delivered by said injection pump bydetaining said second plunger during the suction stroke of said firstplunger at a variable distance from said first plunger, and a furtherresilient stop means for detaining said second plunger on thecompression stroke of said first plunger and to thereby effect that bothplungers are positioned closely one adjacent another at the end of thecompression stroke.

3. Fuel injection device according to claim 1 wherein said adjustablevalve means for mixing fuel and air comprise, a delivery pump housing, adelivery pump member adapted to form a variable pump space, an inductionpipe for the fuel extending to said pump space and having a arrangedreciprocably within said pump housing and r suction valve, a deliverypipe having a delivery valve extending from said pump space to saidinjection pump, and an additional opening in communication with theatmosphere and extending into said pump space having a suction valve foradmixing air to the fuel.

4. An injection pump for fuel injection in internal combustion enginescomprising a housing, cam means operable in said housing, spaced alignedpistons reciprocable in said housing and operable by said cam means,sleeve means connected to one of said pistons, the second piston beingslidable in said sleeve means and being in frictional engagement withsaid sleeve means for common movement therewith during at least a partof the movement of said sleeve means, said sleeve means having a pair ofopenings therein, tension means for the piston connected with saidsleeve means to retract the same to the idling position thereof, stopmeans to limit said common movement of said second piston in bothdirections, the stop means for one direction being adjustable, inletmeans for fuel air mixture entering through one of said openings anddelivery means extending from the other of said openings.

5. A device for fuel injection in an internal combustion enginecomprising a fuel supply, an injection pump including metering means andcompressing means to vary the amount of fuel introduced with each strokeand subject the same to pressure, communicating means between said fuelsupply and said injection pump, and means for admixing air to said fuelin said communicating means, said metering and compressing means beingoperative to displace the fuel and air completely from said compressingmeans upon each stroke.

6. A device according to claim 5, wherein said admixing means isoperative to draw in air into said fuel.

7. A device for fuel injection in an internal combustion enginecomprising a fuel supply and means for delivering fuel from said supplyto said engine including means for initially admixing air to said fuelto produce a fuel mixture, means having variable quantity control meansfor metering said fuel mixture and for subsequently subjecting the sameto pressure, means for completely displacing said metered fuel mixturefrom said last-named means and means for injecting said completelydisplaced metered fuel mixture into said engine.

